Industrial storage batteries, particularly those used for standby emergency power, are often assembled on site from factory-built modules containing multiple cells. For example, if each module contains six 2-volt cells in series to produce 12 volts, a 48 volt battery can be assembled by connecting four modules in series, or a 120 volt battery by connecting ten modules in series. Capacity is usually varied by the number of plates in each cell, with a commensurate increase in the individual cell dimensions. By using such modules, the battery manufacturer can standardize factory production and still satisfy a demand for batteries of various voltage and power requirements.
Examples of such modules will be known to those in the art, such as the Exide Dynacel DC standard and reverse modules. These modules include individual battery cells mounted in an open-faced rectangular steel rack which has internal compartments configured to receive and support the cells in a horizontal row arrangement, although the modules can later be installed to lie horizontally, stand vertically, or be mounted face up in metal stands, whichever is required by the application. The open face allows installation and replacement of the cells in the rack and exposes the cell terminal posts for electrical connection. Conductor bars or cables are used to make electrical connection of the terminals between the adjacent cells in the module. On one of the end cells in the row, the positive polarity terminal or terminals are left unconnected, and on the opposite end cell the negative terminal or terminals are left unconnected. These end cell terminals are then used to make electrical connections between modules to assemble the desired voltage battery on site.
The prior art modules typically have two to six cells, depending upon the size of each cell, which is largely a function of the number of plates in the cell. Larger cells having sixteen or more plates are typically mounted in two or three cell modules, while cells having fifteen or fewer plates are typically assembled in five or six cell modules. The cells are secured in the compartments by bars running along the horizontal top and bottom edges of the open face and overlapping the edges of the cells.
Such prior art modules arrange the cells in a horizontal row in the module rack. To permit the use of shorter conductor bars to reduce resistance losses, the cells are often mounted in the rack in some sort of repeating inverted orientation. For example, in a six cell standard configuration, the positive terminal in the first cell is along one longer side (top) of the horizontal rack and the negative terminal is along the opposite longer side (bottom). The next cell in the row is inverted, such that its positive terminal is next to the negative terminal of the first cell and its negative terminal is next to the positive terminal of the first cell. The third cell in the row is then oriented the same as the first cell. This allows the use of short conductor bars to series connect the three cell sequence. To properly position the end cell terminals, the three cell sequence is repeated in the fourth through sixth cell; that is, the fourth cell and sixth cells have their positive terminal at the top, while the fifth is inverted like the second. A longer "crossbar" conductor bar is then needed to connect the negative of the third cell to the positive of the fourth. In a five cell module, the third cell compartment is left empty to eliminate the crossbar, but a longer connector is still required to bridge the empty compartment.
As the individual cell size is increased by adding additional plates for capacity, the horizontal length of the module increases according to the number of cells. For example, in the Dynacel type DC module, adding two plates per cell increases the six-cell module length approximately 5 inches, but the three cell module length by only approximately 2.5 inches. Such length variations require different length connector bars, and the addition of terminal posts in the higher capacity batteries requires connector bars spanning four or six posts, all combining to require stocking numerous lengths and variations of connector bars for factory assembly of the modules.
A further complication in the prior art modules is that the cells are electrically connected in either standard or reverse terminal configuration with the conductor bars. In standard configuration, the positive terminal(s) of the first cell is left unconnected, while the negative terminal(s) is connected to the positive terminal(s) of the second cell. The negative of the second cell is connected to the positive of the third, and so on to make an internal series connection of cells within the module, with the last cell having an unconnected negative. The unconnected end cell terminals, of opposite polarity, are used to connect modules to assemble a battery. In the reverse configuration, the negative of the first cell, rather than the positive, is the terminal left unconnected. This creates a module of reverse polarity to the standard configuration.
With such horizontal rack modules, modules of the proper polarity must be used next to each other to allow convenient electrical connection between modules. For example, to place a second horizontal module end-to-end to a first module, the modules must be of opposite configuration (i.e., standard and reverse) to avoid the need for a crossbar conductor. To stack a second horizontal module side-by-side on top of a first module, the modules also must be of opposite configuration, otherwise a cable connector must be used to curve around the like polarity terminal of the adjacent cell and reach its opposite polarity terminal. This requires preplanning the number and configuration of modules to be sent to a site for assembly, particularly where floor space or ceiling height requires particular physical dimension limits. Complex installations using many modules often require an assembly drawing of the battery to enable the proper location of the modules, and thereby sacrifice flexibility to make on-site modifications to fit floor space or height limitations.
Further, such prior art modules do not have any rack-to-rack attachment features which automatically align the individual modules in the proper polarity orientation to each other. Channels with matching bolt holes are welded along the horizontal top and bottom of the racks to allow bolted connection of modules, but a module can be improperly matched with a like polarity module, or a like module mounted upside down in an attempt to properly align the end terminals. If the physical connection is done on site by workmen who are not familiar with the electrical connections to be later made by electricians, the battery can be improperly assembled and require reassembly before electrical connection.
These shortcomings are sought to be remedied by the present invention, which also provides other advantages as discussed in the following description.